The 2701HGV-B is used with AT&T's "U-Verse High Speed Internet", which is an ADSL2/2+ product. Also, with this service, the customer owns the modem unlike with the traditional VDSL U-Verse service. Promising so far, but the service isn't ATM-based, it's IP-DSLAM based. From the manual (available here
), it looks like it's usable with ATM and you can set things like the VPI/VCI, but AT&T may have locked that functionality down. If that's the case, you will need to reflash the firmware to a stock 2Wire version.
It may be less of a headache to just buy a new modem.